This invention is directed to an analog video processing scheme for the transmission of multiple television signals. In its preferred embodiment, the invention is more particularly directed to such a system which permits an increase in the transmission efficiency of a satellite transponder used for television program transmission by sending multiple television signals through a single satellite transponder.
This invention is also applicable to other transmission media including, but not limited to, terrestrial broadcasting and cable distribution of TV signals.
Existing approaches can be divided into two categories: one using frequency-division-multiplexing (FDM) techniques for composite or component video signals, and the other using time-division-multiplexing (TDM) of composite video signals. Table 1 summarizes these existing methods, with the right-hand column of Table 1 describing the present invention which will be described herein.
TABLE 1 __________________________________________________________________________ SYSTEMS FOR SATELLITE TRANSMISSION OF TV SIGNALS __________________________________________________________________________ SPECTRAL UTILIZATION FDM TDM OF SPACE SEGMENT SYSTEM APPROACHES HALF-TRANSPONDER NTSC M-NTSC MAC TFM TCM TMVT VIDEO SIGNAL FORMAT CMPST CMPST YUV CMPST CMPST YUV VIDEO BANDWIDTH NONE NONE VERT. NONE 2D OR 2D OR REDUCTION TECHN. CHROMA 3D 3D PROC. PROC. PROC. ARTIFACT Y-C Y-C -- Y-C Y-C REDUC- CROSS- CROSS- CROSS- CRSTLK TION TALK TALK TALK REDUC- OF TION OF DIAG- DIAGON- ONAL AL RE- RESOL- SOLUTION UTION TV CHANNEL FDM FDM FDM TDM TDM TDM MULTIPLEXING METHOD SOUND CHANNEL FM; DIGI- DIGI- DIGI- DIGI- DIGI- TRANSMISSION DIGI- TAL TAL TAL TAL TAL METHOD TAL MULTIPLE-ACCESS YES YES YFS NEEDS NEEDS NEEDS CAPABILITY (2CH) (2CH) (2CH) CONTR CONTR CONTR (2CH) (3CH) (3CH) CONVERSION INTO PAL NEED TO CONV. READY NEED TO CONV. READY & SECAM FROM NTSC INTO YUV FOR INTO YUV FOR SOURCE CONV. CONV. APPLICABILITY TO YES YES YES YES NO YES
& SECAM __________________________________________________________________________
The abbreviations in the above Table should be self-explanatory, e g. with CMPST indicating a composite video signal format and CONTR indicating the need for a controller.
Systems belonging to the first category include the Time-Frequency Multiplexing (TFM) method and the use of half-transponder transmission for an NTSC composite signal (NTSC). a modified NTSC signal(M-NTSC). and Multiplexed Analog Component (MAC) signals. Systems belonging to the second category include the Time-Compression Multiplexing (TCM) method invented by Bell Labs, which uses a bandwidth compression technique for the NTSC composite signal.
Existing FDM/FM techniques for TV transmission via non-linear satellite channels suffer from intermodulation, e.g., intelligible crosstalk. They also require sufficient bandwidth expansion to achieve good signal-to-noise ratio. Therefore it is generally difficult to send more than two TV signals of this type through the same transponder. The TCM method adopts bandwidth compression techniques to allow more TV signals to be transmitted through the same transponder, but the type of bandwidth compression technique used in this system will cause luminance/chrominance crosstalk or interfield flickers which severely degrade the picture quality. Erroneous generation of color information from a black-and-white original picture with high-frequency content is a well-known characteristic of the TCM processing method. As an example the multi-burst test pattern, along with many other types of picture signals cannot be transmitted faithfully.